Winter Groundwater Monitoring

To satisfy planning applications, groundwater monitoring and soil permeability tests are required to determine the ability of underlying soils to accommodate natural drainage during stormwater influx.

Where natural soils are capable of natural drainage, a soakaway is constructed as a lined trench or pre-cast concrete cylinder as a medium for drainage. Where natural drainage is insufficient, engineered drainage systems are utilised instead.

To determine if a soakaway is suitable for a proposed construction, a site investigation is required. This constitutes either a soakaway test in near-surface soils, or permeability tests in boreholes.

Soakaway Testing (Image Above) is undertaken in accordance with BRE Digest 365 for Soakaway Design, or BS5930 for Site Investigation. A trench is excavated which reflects the volume of a proposed soakaway, rapidly filled with water, and monitored over time to determine drop in water level (Image Below).

Measuring the water level in a soakaway trench — Monitoring the drop in water level

A falling-head test can be conducted within boreholes (Image Below) during a geotechnical site investigation. The borehole is filled with water to a known level, and the drop in water level recorded over a nominated time period. Installed standpipes in boreholes are monitored for groundwater a minimum of 3 times during the winter months (Oct – Feb).

A falling-head test to monitor groundwater levels — A falling-head test

drainage geoenvironmental geotechnical groundwater monitoring winter